Process for the preparation of fatty acid esters of sugar glycosides

ABSTRACT

A PREFERABLY SOLVENT-FREE PROCESS FOR THE PREPARATION OF LONG CHAIN FATTY ACID ESTER (C10-C22) OF SUGAR GLYCOSIDES IS DISCLOSED. THE SUGAR GLYCOSIDE ESTERS HAVE UTILITY AS ADDITIVE IN CULINARY MIXES.

Patented Aug. 3, 1971;

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ABSTRACT 01% THE DISCLOSURE A preferably solvent-free process for the preparation of long chain fatty acid-ester (C -C of sugar glycosides is disclosed. The sugar glycoside esters have utility as additives in culinary mixes.

FIELD OF THE INVENTION This invention concerns the preparation of sugar glycoside esters of long chain fatty acids (glycolipids). More particularly this invention concerns a two-step preparation of long chain fatty acid esters of sugar glycosides. Preferably the preparation is solvent-free. These sugar glycoside fatty acid esters are useful as additives in food products and particularly as additives in culinary mixes to improve the batter aeration properties, the eating qualities and the height and volume of cakes prepared from the dry culinary mixes containing these additives.

The process of this invention involves a two-step preparation. In the first step sugar glycoside short chain esters are prepared by reacting a sugar glycoside with a methyl ester of a short chain acid in the presence of an alkali metal alkoxide as a catalyst. For example, the sugar glycoside is reacted with methyl propionate (preferably) or methyl butyrate in the presence of sodium methoxide as a catalyst to produce a mixture of sugar glycoside short chain esters. These sugar glycoside short chain esters are intermediates used in the second step of the process. The sugar glycoside short chain esters are then reacted with a long chain fatty acid ester, as for example, methyl palmitate, in the presence of an alkali metal alkoxide as a catalys tl The reaction which occurs in the second step is a tarnsesterification resulting in the replacement of the short chain acyl group, e.g., propionate or butyrate, by the long chain acyl group, e.g., palmitate, to form the sugar glycoside fatty acid ester.

PRIOR ART Methods of synthesis of long chain fatty acid esters with polyhydric substances are numerous in the art. Martin in U.S. Patent 2,831,855, Tucker in US. Patent 2,831,856, Curtis in US. Patent 2,999,858, Haas et al. in US. Patent 2,893,990, Nobile et al. in US. Patent 3,248,- 381, and US. Patent 3,249,600 all describe the preparation of sugar fatty acid esters in an organic solvent such as dimethylformamide, dimethylacetamide, dimethyl sulfoxide or pyridine using an aliphatic monoor dihydric alcohol ester of a long chain fatty acid and a sugar in the presence of an alkaline catalyst such as alkali metal alcoholates, hydroxides or carbonates. None of the above processes utilizes a solvent-free process involving esterification with a short chain acyl group followed by a transesterification with a long chain acyl group. The prior art processes differ from the present invention in that in the prior art processes no transesterification step is used; a solvent is always used to obtain a homogeneous reaction system; and the sugar glycoside is reacted directly with the long chain fatty acid or their esters.

-In greater detail the process of this invention has the following advantages. In the first step esterification to form the sugar glycoside short chain esters, inethyl alcohol is formed as a result of the esterification. The esterification reaction with the sugar glycoside can be driven to completion by distilling off the methanol asit is formed. In addition the methanol formed can be subsequently used to prepare additional methyl propionate or butyrate where desired. By forming the glycoside propionate or glycoside butyrate ester, the normally hdrophilic sugar glycoside is rendered less hydrophilic. This results in greater miscibility of the sugar glycoside in the long chain ester used in the second step facilitating the formation of the sugar gly coside long chain ester. In the second step of the process, where the long chain fatty acid ester is the methyl ester, methyl propionate or methyl butyrate is formed (depend ing on the short chain acyl group used in the first step) as a result of the transesterification. Either of these by products can be easily and efliciently removed by distilla tion and recycled since they are a reactant in the first step.

Since in a preferred embodiment, the process of this invention is a solvent-free process, this is a decided advantage over prior art methods where the sugar glycoside fatty acid esters are to be ultimately used in food products. For example, where high boiling solvents such as dimethylformamide, dimethylacetamide, dimethyl sulfoxide, etc., are used, as in prior art methods, it is difiicult to ensure that all of the solvent is removed from the product because these solvents are high boiling. Thus the process of this invention offers an advance over prior are methods in that purification of the sugar glycoside ester is quite easy because the methyl alcohol by-product formed in the first step and the short chain ester lay-product formed in the second step are low boiling materials and can be easily and completely removed. As a result of this, the process of this invention can be advantageously employed to produce sugar glycoside fatty acid esters which are to be used in edible products such as culinary mixes or shortenings.

DESCRIPTION OF THE INVENTION This invention involves a process for the preparation of long chain fatty acid esters of sugar glycosides. The process of this invention comprises the steps of (l) reacting a sugar glycoside selected from (a) aldose glycosides having the formula wherein A is selected form the group consisting of hydrogen, -CH OH, -CHOH-CH OH, wherein B is selected from the group consisting of hydrogen and 0 -CH OH, and wherein D is selected fromthe class consisting of alkyl groups having from 1 to 4 carbon atoms, hydroxyalkyl groups having from 2 to 3 carbon atoms,

wherein is: an integer and ranges from 1 to 4, and

glycosyl groups having from about 5 to about 18 carbon atoms; with a. short chain ester selected from the group consisting of methyl propionate and methyl butyrate in the presence; of an-alkali metal alkoxide having from 1;to,3 carbon atomsto form a sugar glycoside short chain ester,and (2)- reacting the short chain ester of Step (1) with along ;.chain ester of the formula R OR wherein R ,is an acyl group having from about to about 22 carbon atoms and where R is an alkyl group having from 1 to about 3 carbon atoms, in the presence of an alkali metalalkoxide havingfrom 1 to 3 carbon atoms to form asugar glycoside long chain ester; said process steps being conducted at a temperature of from'about 60 C. to about 11.0"- C. k I I The process of this invention is very simple and straight forward to carry out. It is necessary to use only the re actants in the process and the catalyst involved. No solvent is necessary to convert the sugar glycoside into a sugar glycoside fatty acid ester. In the process of this invention the hydroxyl groups present within the anhydrosugar unit and the aglycone moiety (if hydroxyl containing) are esterified in Step (1) with short chain acyl groups. The intermediate sugar glycoside short chain esters are soluble in the fatty acid esters used in Step (2) and the mutual solubility results in a homogeneous system eliminating the need for a solvent. These short chain acyl groups in the intermediate sugar glycoside ester are subsequently displaced (i.e., by transesterification) in Step (2) resulting in the replacement of the short chain acyl group of Step (1) with a long chain fatty acyl group of Step (2). Both Step 1) and Step (2) of the process of this invention are schematically shown below.

l Alkali MetalAlkoxide Sugar Glycoside Methyl Propionate Sugar Glycoside Propionate Ester Methanol Sugar Glycoside Fatty Acid Ester Alkyl Propionate Sugar glycosides The sugar glycosides which can be used in the process of this invention are compounds having an anhydrosugar unit and an aglycone moiety. The anhydrosugar unit can be radicals derived from any of the pentoses, hexoses, and heptoses. In addition,,radicals derived from both aldoses and ketoses can be used in the process of this invention.

The radicals which can be used as the anhydrosugar unit in the process of this invention are radicals derived from the following sugars: pentoses such as ribose, arabinose, cyclose,xylose, and lyxose, hexoses such as allose, altrose, glucose, mannose, gulose, idose, galactose, talose, fructose, and sorbose; and heptoses such as glucoheptose, galaheptose, mannoheptose and perceulose. As can be seen from examination of suitable sugars which can be used in the process of this invention the stereochemical (optical) configuration of the anhydrosugar unit is immaterial. Other sugar radicals can be selected based on the disclosure given above which will be suitable for the purposes of this invention without departing from the scope and spirit of .this invention.

' Theradicals derived from glucose, fructose, galactose, and sorbose,'e.g., where A is -CH OH and B is H, are preferred as the anhydrosugar unit because the sugars from whence they can be obtained are commercially available.

In addition radicals derived from oligosaccharides can be used as the anhydrosugar unit in the process of this invention and are included within the spirit and scope of this invention. Suitable examples of such oligosaccharides are lactose, maltose and the dextrans. Lactose and maltose are preferred.

Aglycone moiety As has been hereinbefore described the sugar glycoside contains an anhydrosugar unit and an aglycone moiety. On examination ofthe above formula it can be seen that the aglycone moiety of the sugar glycoside is represented by the letter D. The aglycone moiety, D, can be an alkyl group having froml to 4 carbon atoms. Where D is an alkyl group, suitable alkyl groups are methyl, ethyl, propyl, iso-propyl, butyl, and iso-butyl.D can also be a hydroxyalkyl group having from 2 to 3 carbon atoms. Examples of suitable hydroxyalkyl groups are hydroxy ethyl and hydroxypropyl.

D can also be a radical derived from a polyhydric alcohol having the formula wherein x is an integer which ranges from l to about 4 and is preferably 1. Examples of such suitable polyhydric radicals which can be used as the aglycone portion of the sugar glycosides are radicals derived from the following polyhydroxy alcohols: e.g., glycerol, allitol, dulcitol, ribitol, erythritol, xylitol, sorbitol, mannitol, glucitol, talitol, lyxitol, galactitol, rhamnitol, iditol, and talitol.

D in the general formula can be a glycosyl group. Where D in the general formula above is a glycosyl group, the glycosyl group is not usually considered to be an aglycone moiety by sugar chemists. That is to say, in the nomenclature used in sugar chemistry, the aglycone moiety is considered to be something other than an anhydrosugar unit or glycosyl group. For simplicity in the disclosure of this invention, the term aglycone moiety includes glycosyl groups in addition to the other aglycone moieties described hereinbefore. WhereD is a glycosyl group, e.g., an anhydrosugar unit, the sugar glycoside is an oligosaccharide. For example, if the aldose (a) above is glucose and if D is a fructosyl group, the glycoside is sucrose. The oligosaccharides, e.g., where D in the above formula is a glycosyl group (anhydrosugar unit), which can be used in the process of this invention are oligosaccharides such as sucrose, railinose and stachyose.

It is preferred that the aglycone moiety D be methyl or ethyl because the methyl and ethyl glycosides are commercially available or that the aglycone moiety be the radical derived from glycerol since the glycosylglycerols are easily prepared. Where the aglycone moiety is a glycosyl group, sucrose is preferred because of itspurity, ready availability and cost.

Fatty acid esters The fatty acids which can be used in the fatty acid esters of Step (2) of the process of this invention, i.e., in the transesterification step, are fatty acids having from about 10 to about 22 carbon atoms in the chain, preferably from about 14 to about 22 carbon atoms. The short chain esters of these fatty acids containing from 1 to about 3 carbon atoms, e.g., the methyl, ethyl, and propyl esters, are the preferred fatty acid esters. The methyl esters of the fatty acids are normally used and are preferred be: cause the methyl propionate or methyl butyrate formed in Step (2) can be easily removed and recycled for use acids of comparable chain lengths, e.g., about to about 22 carbon atoms, can also be used and are included within the scope of this invention. Although both unsaturated and saturated fatty acids can be usedin the process of this invention, the saturated fatty acids are preferred because they are more eflicient additives when used in culinary mixes and result in increased cake heights and volumes.

Esterification catalyst In both Step (1) and Step (2) of the process described hereinbefore for the production of fatty acid esters of the sugar glycosides, the catalyst which can be used is an alkali metal alkoxide having from 1 to about 3 carbon atoms. Specifically, the sodium, potassium and lithium methoxides, ethoxides and propoxides are suitable for the process of this invention. The methoxides are especially desirable because of cost and availability. Sodium methoxide is most preferred. The alkali metal alkoxide catalyst can be used in a molar ratio of from about 1: 100 to about 1:5 to the sugar glycoside. A preferred range is from about 1:50 to 1:10.

Process conditions The process of this invention can be carried out in any type of reaction vessel in which the reactants can be warmed in the presence of the alkoxide catalyst and the by-products formed removed by distillation. In Step (1) the temperature of operation can range from 60 C. to about 110 C. and is preferably at the reflux temperature of the mixture of methyl propionate (or butyrate) and the sugar glycoside to be esterified. This temperature is normally about 80 C. for methyl propionate and 102 C. for methyl butyrate. In the second step of the process the temperature of operation can range from about 60 C. to about 110 C. In addition, it is desirable, although not required, to conduct the transesterification of Step (2) in vacuo, preferably 700 mm. to 20 mm., to facilitate the removal by distillation of the methyl propionate or methyl butyrate formed. Low reaction temperatures are preferred because-there is less degradation of reactants and products than is the case with higher temperatures. The molar ratio of the sugar glycoside to the short chain ester of Step (1) is from about 1:1 to about 1:100, preferably about 1:5 to about 1:15, while in Step (2) the molar ratio of the sugar glycoside short chain ester reaction product of Step (1) to the long chain fatty acid ester is dependent on the number of hydroxyl groups in the original sugar glycoside and ranges from about 1:1 to about 1:20, preferably 1:4 to about 1:10. The sugar glycoside long chain ester can be separated and purified using techniques well known in the art, e.g., solvent extraction procedures, using chloroform/water in which the organic solvent is separated and evaporated to dryness to yield the sugar glycoside ester.

The process of this invention can also be carried out as a one-step process in which the methyl propionate or methyl butyrate of Step (1) is used with the short chain alcohol fatty acid ester of Step (2). The sugar glycoside ester will preferentially react with the methyl propionate or butyrate forming the sugar glycoside propionate or butyrate ester and methyl alcohol. Again the reaction can be driven to completion by distilling off the methyl alcohol formed. The sugar glycoside propionate or butyrate ester than reacts with the short chain alcohol long chain ester to form the sugar glycoside long chain ester and methyl propionate or methyl butyrate. As can be seen the course of the reaction is the same regardless of whether the reaction is conducted as a two-step or a onestep process.

I Utility The sugar glycoside esters formed by the process of this invention have utility as additives in culinary mixes. As is well known in the art, dry prepared culinary mixes contain additives to accomplish a specific purpose and make the baked cake better. For example, emulsifiers are old and well known in the art and are normally incorporated into the shortening of culinary mixes. Emulsifiers facilitate the formation of an oil and water emulsion and when used in a dry culinary mix the result is better batter aeration during mixing, improved eating qualities in the prepared cake and improved volume of the prepared cake.

The sugar glycoside fatty acid esters prepared by the process of this invention can be used in a dry culinary mix formation or can be incorporated into shortenings or the shortening portion of a dry culinary mix to improve the batter aeration properties of the mix when prepared by the housewife and to obtain better cake height and volume. The effect of the sugar glycoside fatty acid esters prepared by the process of this invention when used as additives in a dry cake mix will be apparent on examination of the Examples given hereinafter and in addition in the Examples given in my copending application Ser. No. 746,774, filed July 23, 1968, filed simultaneously herewith.

EXAMPLE I Preparation of methyl a-D-glucoside tetrapalmitate Step (1). A suspension of methyl oc-D-glllCOSide (19.4 g.) in methyl propionate (250 ml.) containing sodium methoxide (0.25 g.) as the catalyst was heated to reflux (approximately C.) and stirred during which time the methanol formed in the reaction was slowly distilled from the reaction mixture. More sodium methoxide was added as needed (approximately 0.25 g.). After about 12 hours all of the methyl ot-Dgll1COSiCl6 had dissolved during which time the reaction was driven to completion by distilling off the methanol formed. The excess methyl propionate was then removed by distilla tion. Thin layer chromatography of the residual material indicated the presence of a mixture of methylot-D-glucoside mono-, di-, tri-, and tetrapropionates.

Step (2). Methyl palmitate (108 g.) and sodium methoxide (0.25 g.) were added to the methyl oc-D-gl11- coside propionate esters prepared in Step (1) above and the mixture was heated at C. under vacuum (aspirator, approximately 20 mm.) with stirring for 10 hours. The methyl propionate formed as a by-product was distilled off. Water and chloroform were added to the cooled residue and the mixture was shaken in a separatory funnel. The chloroform layer was removed and evaporated on a rotary evaporator to yield methyl wD-glUCOSid tetrapalmitate.

EXAMPLE II Preparation of methyl a-D-glucoside tetrabehenate The procedure of Example I was followed except that 144 g. of methyl behenate was substituted for the methyl palmitate in Step (2) of Example I. Methyl u-D-glucoside tetrabehenate was obtained on workup.

When in Examples I or II above methyl butyrate is substituted on an equivalent basis for the methyl propionate used in Step (1) of Examples I or II, substantially equivalent results are obtained in that methyl rx-D- glucoside tetrapalmitate or methyl ot-D-glucoside tetrabehenate is obtained.

When in Examples I or II above other alkali metal alkoxides, e.g., sodium, lithium or potassium ethoxide or propoxide are substituted on an equivalent basis as the catalyst for the sodium methoxide used in Example I and II above substantially equivalent results are obtained in that methyl a-n-glucoside tetrapalmitate or methyl a-D-glucoside tetrabehenate is obtained.

When in Examples I or II above other alkyl fatty acid esters are substituted on an equivalent basis for the methyl palmitate of Example I or the methyl behenate of Example II substantially equivalent results are obtained in that the corresponding sugar glycoside fatty acid esters are obtained, e.g., methyl caprate, ethyl laurate, propyl stearate, methyl myristate, and ethyl arachidate.

When in Examples I and II above other glycosides are substituted on an equivalent basis for the methyl oc-D- glucoside, substantially equivalent results are obtained in that the corresponding sugar glycoside palmitate or behenate esters are prepared: e.g., ethylglucoside, propylglucoside, butylglucoside, hydroxyethylglucoside, hydroxypropylglucoside, glucosylglycerol, glucosylmannitol, glucosylsorbitol, methylgalactoside, ethylgalactoside, hydroxyethylgalactoside, galactosylglycerol, methylarabinoside, ethylarabinoside, hydroxyethylarabinoside, arabinosylglycerol, arabinosylmannitol, methylsorboside, ethylsorboside, hydroxyethylsorboside, sorbosylglycerol, sorbosylmannitol, methylguloside, ethylguloside, propylguloside, hydroxyethylguloside, gulosylglycerol, gulosylsorbitol, methylfructoside, ethylfructoside, propylfructoside, hydroxyethylfructoside, butylfructoside, fructosylglycerol, fructosylsorbitol, methylrhamnoside, ethylrhamnoside, propylrhamnoside, hydroxyethylrhamnoside, rhamnosylglycerol, rhamnosylmannitol, methylxyloside, ethylxylo side, hydroxypropylxyloside, propylxyloside, xylosylglycerol and xylosylmannitol.

When in Examples I and II above sucrose, rafiinose or stachyose are substituted on an equivalent basis for the methyl a-D-glucoside, substantially equivalent results are obtained in that sucrose, raflinose or stachyose palmitate or behenate esters are prepared.

When in Examples I and II above the methyl propionate formed in Step (2) is recycled as a reactant in Step (1), substantially equivalent results are obtained in that methyl oc-D-glllCOSid6 tetrapalmitate or methyl a-n-glucoside tetrabehenate is prepared.

Sugar glycoside fatty acid esters prepared by the process of the invention as additives in dry prepared yellow cake mix Dry layer cake mixes were prepared by blending together thoroughly sugar, flour, and shortening in a conventional hea'vy-duty mixer, and passing this blend through a standard roller mill. After the milling step, the minor ingredients shown below in Table I in addition to the sugar, flour and shortening were added to the mixture. The mixture was then subjected to an impact grinding to break up any agglomerates or large particles present.

TABLE I.-YELLOW CAKE MIX-BASIC COMPOSITION Percent by weight Ingredient: of dry mix Sugar (industrial, fine, granulated sucrose and dextrose) 43.77

Flour (soft wheatcake fiuor) 40.48

Shortening (a mixture of tallow and directly rearranged lard hydrogenated to an iodine value of about 55) 11.0 Non-fat dried milk solids 1.50

(Soda -1 0.90 Salt 0.75 Sodium acid pyrophosphate 0.84 Monocalcium phosphate 0.36 Carboxymethylcellulose 0.20 Flavoring 0.20

The shortening used in the above described yellow cake mix formulation was prepared by mixing the sugar glycoside fatty acid esters and the shortening emulsifiers at the indicated level with the shortening base stock prior to the incorporation of the shortening into the yellow cake mix formulation. The sugar glycoside esters and emulsifiers which were used in the shortening portion of the yellow cake formulation are described in Table II below. The cake heights shown in Table II were obtained by baking a cake from the prepared yellow cake mix. The yellow cake dry mix (540 g.) was rnixed with 320 ml. of water and 96 g. of whole egg in a home style mixer for 2 min- TABLE II.SUGAR GLYCOSIDE ESTERS AS CAKE MIX ADDITIVES Shortening composition Sugar Shortening glycoside Cake height, base stock e LAE b ester center/edge (percent) (percent) (percent) (inches) e A mixture of tallow and directly rearranged lard hydrogenated to an iodine value of about 55.

Esters of lactic acid and monoand/0r diglycerides containing saturated fatty acid groups having from about 12 to about 22 carbon atoms.

(1) Methylglucoside tetrapalmitate.

(2) Methylglucoside tetrabehenate.

All of the above cakes, with the exception of the control, Cake H, had acceptable eating qualities.

As can be seen from examination of the cake heights shown in the above table, the sugar glycoside fatty acid esters when used as an additive (Cakes A-G) in the shortening portion 0 a yellow cake mix increased the cake height obtained over that obtained with no additive (Cake H) in the shortening used in the cake mix. In addition as can be seen from Table II above, the sugar glycoside fatty acid esters when used in combination with a well-known shortening emulsifier (LAE) results in an increase cake height over that obtained with no shortening additive or emulsifier (Cake H).

What is claimed is:

1. A process for the preparation of sugar glycoside long chain esters comprising the steps of:

( 1) reacting a sugar glycoside selected from the group consisting of:

(a) aldose glycosides having the formula and, (b) ketose glycosides having the formula CH OH D-O-C JHOH JHOH O CHOH wherein A is selected from the group consisting of hydrogen, CH OH, and

atoms, radicals derived from polyhydric alcohols having the formula 011 HO CH2GCDCH20H wherein X is an integer and ranges from 1 to 4, and glycosyl groups having from about 5 to about 18 carbon atoms; with a short chain ester selected from the group consisting of methyl propionate and methyl butyrate in the presence of alkali metal alkoxide having from 1 to 3 carbon atoms and in the absence of a solvent; to form a sugar glycoside short chain ester and methyl alcohol, wherein said methyl alcohol is removed by distillation; and

(2) reacting the sugar glycoside short chain ester of Step (1) with a long chain ester of the formula R OR wherein R is a fatty acid group having from about 10 to about 22 carbon atoms and wherein R is an alkyl group having from 1 to about 3 carbon atoms, in the presence of an alkali metal alkoxide having from 1 to 3 carbon atoms to form a sugar glycoside long chain ester; Step (2) being conducted under a vacuum; the short chain methyl ester which is formed being removed by distillation; and said process steps being conducted at a temperature of from about 60 C. to about 110 C.

2. The process of claim 1 wherein the sugar glycoside .and the short chain ester of Step (1) are present in a molar ratio of 1:1 to 1:100; wherein the sugar glycoside short chain ester and the long chain ester of Step (2) are present in a molar ratio of 1:1 to 1:20; and wherein the alkali metal alkoxide is present in a molar ratio of 12100 to 1:5 to the sugar glycoside.

10 3. The process of claim 2 wherein Step (1) is conducted at reflux temperature and the short chain methyl ester distilled in Step (2) is recycled for use in Step (1). 4. The process of claim 3 wherein the alkali metal alkoxide is sodium methoxide.

5. The process of claim 4 wherein A is --CH OH, wherein B is hydrogen and wherein D is a radical derived from a polyhydric alcohol having the formula wherein x is 1, wherein the short chain ester is methyl propionate, wherein R has from about 14 to about 22 carbon atoms, and wherein R is methyl.

6. The process of claim 5 wherein D is selected from the group consisting of methyl and ethyl.

7. The process of claim 6 wherein D is a glycosyl group having from about 5 to about 7 carbon atoms.

LEWIS GOTTS, Primary Examiner J. R. BROWN, Assistant Examiner US Cl. X.R. 260-2l0 

